The effect of enzyme concentration and serum concentration on initial rate measurements of serum enzymes

The correlation between measured enzyme activity and enzyme concentration has been tested for aspartate aminotransferase and creatine kinase. Some conditions where this is non-linear have been described. The correlation was independent of the source of the enzyme: serum enzymes or purified enzyme solutions. By isotope technique a back reaction has been demonstrated for aspartate aminotransferase. Difficulty of measuring true initial reaction rates in manual routine methods has been demonstrated. When methods with a non-linear correlation curve have to be used, the estimation of serum concentration of enzyme must be based on a correlation curve between enzyme concentration and enzyme activity.